Staging: comedi: add ssv_dnp driver

driver for SSV Embedded Systems' DIL/Net-PCs

From: Robert Schwebel <robert@schwebel.de>
Cc: David Schleef <ds@schleef.org>
Cc: Frank Mori Hess <fmhess@users.sourceforge.net>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>